Revisions to Accelerated Corrosion Test Method for Post-Tensioning Grout

Abstract

A minimum degree of corrosion protection should be conferred to an embedded prestressing strand by post-tensioning grouts, along with placement-related requirements. The accelerated corrosion test (ACT), an anodic polarization test procedure, is currently used to measure corrosion protection in the United States. Approval of a specific grout currently requires two conditions: a 1,000 hour average ACT time-to-corrosion minimum result; and a 0.45 water-cement ratio standard mixture (only water and portland cement) less than or equal to an ACT time-to-corrosion result tested under the same conditions. Different combinations of the two approval conditions are used in various specifications. Criticism has resulted since the ACT test procedure does not currently require that grout resistance variations be accounted for during selection of applied voltage. The addition of admixtures and pozzolans can significantly vary grout resistance, perhaps affecting test results adversely. The authors report on research on different ACT test post-tensioning grout mixtures with admixture level variation and resistivity effects inherent to electrochemical systems compensation option. Study results show that resistivity variation significantly affected test type variation, so when testing equipment does not allow IR compensation, potentially lower quality grouts may occur.